JP2006238496A - Saw filter package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fully increase the amount of attenuation caused by a change in a formed attenuation pole not only in a high-band attenuation band, but also in a low-band one regardless of a miniaturized configuration. <P>SOLUTION: An SAW filter package comprises: a first electrode; a second electrode; a third electrode; a fourth electrode; a piezoelectric substrate on which a first SAW resonator connected between the first and second electrodes, a second SAW resonator connected between the first and third electrodes, and a third SAW resonator connected between the second and fourth electrodes are formed; a package having a plurality of package electrodes and mounting the piezoelectric substrate; and a group of bonding wires constituted of a plurality of bonding wires, wherein the third and fourth electrodes are connected via the group of bonding wires, and the third and fourth electrodes are connected with an electrode to which ground potential is supplied, among said package electrodes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a SAW filter package, which is suitable for application to a SAW filter package having a SAW filter for transmission or reception used in a small mobile communication device such as a mobile phone.

  Documents describing this type of polarized SAW filter include the following Patent Documents 1 and 2 and Non-Patent Document 1.

  In recent years, development of mobile communication device terminals such as small and lightweight mobile phones has been rapidly advanced. Along with this, there is a demand for miniaturization and high performance of components used, and development of RF components (high frequency components) based on surface acoustic wave (SAW) elements is required.

  A basic circuit configuration of the ladder-type SAW filter described in Non-Patent Document 1 is shown in FIG.

  The ladder-type SAW filter shown in FIG. 2 is a device that greatly contributes to the miniaturization of the RF section, and hence its practical application is strongly desired. RF devices such as SAW duplexers using this ladder-type SAW filter have already been developed and are partly put into practical use.

  The characteristics (attenuation characteristic (1) and return loss characteristic (2)) of the 800 (MHz) band ladder type SAW filter of FIG. 2 are shown in FIG. The filter characteristics in FIG. 3 correspond to the case where the cross length of the series arm resonator is 100 μm and the logarithm is 100, the cross length of the parallel arm resonator is 70 μm, and the logarithm is 70.

  4 also shows the characteristics of the series arm resonator and the parallel arm resonator of FIG. 3 (that is, the imaginary part characteristic of the series arm resonator is jx, the imaginary part characteristic of the parallel arm resonator is jb, The real part characteristic is rs, and the imaginary part characteristic of the parallel arm resonator is rp).

  The attenuation pole of the high band side attenuation band in the pass band shown in FIG. 3 (the frequency band near 863 MHz to 911 MHz) is the frequency of the series arm resonator circuit at an infinite point (that is, about 42 dB) (that is, near 919 MHz). It can be seen from the comparison between FIG. 4 and FIG. 3 that the attenuation pole in the low-frequency side attenuation region occurs at a frequency where the parallel arm resonator circuit is zero (ie, near 855 MHz).

  FIG. 3 also shows the real part of the circuit of each SAW resonator when Q = 500.

  As can be seen from the characteristics of FIG. 3, the ladder-type SAW filter of FIG. 2 has one attenuation pole in the low-pass attenuation band and one in the high-pass attenuation band. It is known that the characteristics of the attenuation band and the characteristics of the high band side attenuation band have substantially the same characteristics.

  However, with the rapid increase in demand for mobile communication device terminals, both the mobile communication system using the 800 (MHz) band frequency band and the mobile communication system using the 2 (GHz) band frequency band have the transmission band and The reception band is wide and the interval between the transmission band and the reception band is set narrow.

  As an example, when the transmission band is 824 to 849 MHz and the reception band is 869 to 894 MHz, as in the US CDMA (Code Division Multiple Access) system, the reception band is in the high band side attenuation band of the transmission band. The attenuation of the low band attenuation band of the transmission band may not be so large because it is located, but if the attenuation of the high band attenuation band is not sufficiently large, the mobile communication device terminal transmitted There is a high possibility that the radio wave leaks into its own reception band and deteriorates the reception quality.

  3 is viewed from this point of view (considering that the characteristic curve is shifted to the left side (low band side) in FIG. 3), the filter characteristic of FIG. 3 shows that the attenuation amount is the same as the low band attenuation band. Since it is the same and approximately −10 dB, the amount of attenuation on the high frequency side is not necessarily sufficient.

  On the other hand, for example, in Patent Document 1 (or Patent Document 2), the filter characteristics as shown in FIG. 5 can be obtained using the SAW filter having the structure shown in FIG. The SAW filter of FIG. 6 has the ladder-type SAW filter CP1 of FIG. 2 and one L (inductor LX) two-terminal pair circuit CP2, and is configured by connecting these two two-terminal pair circuits CP1 and CP2 in series. This is a polarized SAW filter LA.

  In FIG. 5, mark ▽ 1 indicates a point with a frequency of 818 MHz and attenuation −3.0609 dB, mark Δ 2 indicates a point with a frequency 843 MHz and attenuation −2.9886 dB, and mark Δ 3 indicates a frequency 863 MHz and attenuation − A point of 43.794 dB is shown, and a mark Δ4 shows a point of frequency 888 MHz and attenuation −38.099 dB.

As is apparent from FIG. 5, if the SAW filter having the filter characteristics of FIG. 5 is applied to the transmission band of the CDMA system in the United States, the amount of attenuation in the high band side attenuation band is sufficiently large. Therefore, good communication quality can be obtained for both transmission and reception.
JP-A-10-93382 JP-A-10-163808 Low loss band filter using SAW resonator: Sato, Igata, Miyashita, Matsuda, Nishihara: IEICE Transactions A, Vol. J76-A, no. 2, pp 245-252, 1993.

  However, even with the filter characteristics of FIG. 5, it cannot be said that the attenuation amount in the low-frequency side attenuation band is sufficiently large. Therefore, in the above-described example of the US CDMA system, the SAW filter of Patent Document 1 is applied as a reception filter. However, the filter characteristics are not always sufficient, and the reception quality may deteriorate.

  That is, in the example of the CDMA method described above, when a filter that does not have good characteristics, such as the SAW filter of Patent Document 1, is used as a transmission filter, leakage from the transmission side of the mobile communication device terminal. The reception filter cannot sufficiently reduce the effects of interference, and even when there is an interference wave effect coming from a wireless communication device other than the mobile communication device terminal. It cannot be reduced.

  Depending on the system, the transmission band may be set to be higher in frequency than the reception band, contrary to the US CDMA system described above. In this case, the transmission filter and the reception band may be set. It is necessary to replace the filter for use.

  Regardless of whether it is a transmission filter or a reception filter, the problem to be solved by the present invention is as follows when attention is paid to the operation principle of the polarized SAW filter of Patent Document 1 and Patent Document 2. Can be expressed.

  In the conventional polarized SAW filters described in Patent Documents 1 and 2 and the like, an attenuation pole is formed within a finite frequency by one L two-terminal pair circuit. The amount is small in the low-band attenuation band of the pass band, and is large in the high-band attenuation band of the pass band. Therefore, even if the required standard of the high attenuation amount of the high band side attenuation band of the pass band can be satisfied, there is a high possibility that the required standard of the low band attenuation band of the pass band cannot be satisfied.

  If the L value of the inductance LX in FIG. 6 is set to be extremely large, it can be considered that the attenuation amount of the high-frequency side attenuation band can be sufficiently increased, but such a large L value is It is difficult to realize.

  Further, when the interval between the attenuation band and the pass band (for example, the interval between the transmission frequency band and the reception frequency band for the same mobile communication terminal) is about 20 (MHz) as described above, it is steep. Filter characteristics are required.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a SAW filter package that can satisfy the required standard in the low-pass attenuation band of the pass band.

  In order to solve such a problem, the SAW filter package of the present invention includes a first electrode, a second electrode, a third electrode, a fourth electrode, the first electrode, and the second electrode. A first SAW resonator connected between the second electrode, a second SAW resonator connected to the first electrode and the third electrode, the second electrode, and the fourth electrode. A piezoelectric substrate on which a third SAW resonator connected to the substrate is formed, a package having a plurality of package electrodes and mounting the piezoelectric substrate, and a bonding wire group consisting of a plurality of bonding wires. And the third electrode and the fourth electrode are connected via the bonding wire group, and a ground voltage is supplied from the third electrode, the fourth electrode, and the package electrode. The connected electrode And it features.

  As described above, according to the present invention, a plurality of attenuation poles are formed in the high band side attenuation band and the low band side attenuation band of the pass band of the polarized SAW filter. However, the amount of attenuation due to the change of the formed attenuation pole can be sufficiently increased not only in the high-frequency attenuation band but also in the low-frequency attenuation band.

(A) Embodiment Hereinafter, an embodiment of a SAW filter package according to the present invention will be described.

  In general, in a SAW filter, if a large number of SAW resonators are used, an ideal filter characteristic that has a sufficiently large attenuation amount in both the low-band attenuation band and the high-band attenuation band of the pass band and is steep. However, it is possible to obtain a good filter characteristic close to such an ideal filter characteristic by using a SAW filter that is as small as possible using as few SAW resonators as possible. is important.

  The SAW filter is mainly used from the viewpoint of miniaturization, such as a mobile terminal device for mobile communication using a frequency band of 800 (MHz) and a mobile terminal device for mobile communication using a frequency band of 2 (GHz). It is being used frequently as an RF filter.

(A-1) Configuration of First Embodiment FIG. 1 shows a circuit diagram of a SAW (Surface Acoustic Wave) filter 10 of this embodiment. The SAW filter 10 functions as a reception filter for a mobile phone in the above-described US CDMA system, for example. Of course, it can also be used as a transmission filter if necessary.

  In FIG. 1, the SAW filter 10 includes input terminals IN and GND1, output terminals OUT and GND2, three SAW resonators SR1, PR1 and PR2, three inductances L1 to L3, and six connection points P1 to P1. P6.

  Among these, the SAW resonator SR1 is a series arm SAW resonator disposed between the input terminal IN and the output terminal OUT and provided in the series arm having the connection points P3 and P4.

  The SAW resonator PR1 (110) is a parallel arm SAW resonator provided in a parallel arm having the connection point P3 and the connection point P1, and similarly, the SAW resonator PR2 (111) This is a parallel arm SAW resonator provided on a parallel arm having a connection point P4 and a connection point P2.

  An inductance L2 (131) is connected between the connection points P1 and P2.

  Further, connection points P5 and P6 are provided between the input terminal GND1 and the output terminal GND2, and an inductance L1 (130) is connected between the connection point P1 and the connection point P5, and the connection point P2 An inductance L3 (132) is connected between the connection points P6.

  That is, the poled SAW filter 10 has components P1, P2, P5, P6, L1 to L3, GND1, GND2 with respect to the two-terminal pair circuit 30 having the components IN, P3, P4, SR1, PR1, PR2. The two-terminal pair circuit 31 having the above is connected in series.

  L1 to L3 are also used as values indicating the L value of each inductance as necessary.

  FIG. 11 shows an implementation example corresponding to the circuit diagram of FIG. FIG. 11 shows a SAW filter package 10A realized by a microfabrication technique similar to a normal IC (semiconductor integrated circuit).

  In FIG. 11, the SAW filter package 10 </ b> A includes pads 12 and 16 formed on the package 11 and a piezoelectric substrate 21.

  SAW resonators 100, 110, and 111 are connected to, for example, tungsten electrodes 14A and 14B that are provided on the piezoelectric substrate 21 and have a "π" shape, for example.

Among these, the SAW resonator 100 includes two grating reflectors 100A and 100C, and an interdigital electrode (interdigital converter: IDT) 100B disposed therebetween.

  The comb-like electrode 100BA constituting the interdigital electrode 100B is electrically connected to the electrode 14A, and the other comb-like electrode 100BB constituting the interdigital electrode 100B is electrically connected to the electrode 14B. It is connected to the.

  The structure of the resonators other than the SAW resonator 100 is the same as this. The SAW resonator 110 includes two grating reflectors 110A and 110C, and an interdigital electrode 110B disposed therebetween, and includes the SAW resonator 111. Comprises two grating reflectors 111A and 111C and an interdigital electrode 111B arranged between them.

  Further, the comb-like electrode 110BA constituting the interdigital electrode 110B is electrically connected to the electrode 14A, and the other comb-like electrode 110BB constituting the interdigital electrode 110B is connected to the pad P22 (see above). (Corresponding to P1).

  Similarly, the comb-like electrode 111BA constituting the interdigital electrode 111B is electrically connected to the pad 23 (corresponding to P2), and another comb-like electrode 111BB constituting the interdigital electrode 111B. Are electrically connected to the electrode 14B.

  However, in this embodiment, the crossing lengths and logarithms of the SAW resonators SR1, PR1, and PR2 are as shown in FIG.

  That is, the cross length of the series arm resonator SR1 is 55 μm and the logarithm is 100, the cross length of the parallel arm resonator PR1 is 66 μm, the logarithm is 66, the cross length of the parallel arm resonator PR2 is 66 μm, and the logarithm is 66. It is a book.

  The pad 12 and the electrode 14A in FIG. 11 are connected by a bonding wire 13 having a sufficiently small amount of inductance, and the pad 16 and the electrode 14B are connected by a bonding wire 15 having a sufficiently small amount of inductance. The bonding wires 17 (corresponding to L1), 18 (corresponding to L2), and 19 (corresponding to L3) each have a desired L value.

  In the present embodiment, the L value of each of the bonding wires 17 to 19 is assumed to be the same value (for example, 0.1 nH).

  Compared to the conventional SAW filter shown in FIG. 6 at the level of the circuit diagram, the SAW filter 10 of the present embodiment is different in the structure of the two-terminal pair circuit 31.

  The operation of the present embodiment having the above configuration will be described below.

(A-2) Operation of the First Embodiment FIG. 12 shows a bisected circuit diagram of the polar SAW filter 10 of the present embodiment.

  FIG. 13 is a lattice equivalent circuit diagram for explaining the operation of the polarized SAW filter 10.

  A ladder-type SAW filter 10 shown in FIG. 1 has a two-stage π-type configuration including three SAW resonators (SR1 (100), PR1 (110), and PR2 (111)). On the other hand, a two-terminal pair circuit 31 composed of three L (L1 (130), L2 (131), L3 (132)) is connected in series.

  Here, in order to evaluate the operation of the polarized SAW filter 10 of FIG. 1 and to obtain the relationship between the attenuation pole frequency of the polarized SAW filter 10 and the L value, the bisection circuit of FIG. 12 is used.

  The input impedance of the circuit at the time of opening the terminals (OUT (1), OUT (2), E) of the bisection circuit of the bisection circuit of FIG. 12 is ZF, and the terminal of the bisection circuit (OUT (1)) , OUT (2), E) and ZF, ZS is given by Equation (1) and Equation (2), where ZS is the input impedance of the circuit at the time of short circuit.

ZF = Z (PR1 (110)) + jωL1 (130) (1)
ZS = 1 / ((1 / Z (SR1 (100)) + 1 / (1 / Z (PR1 (110)) + jω (1 / (1 / L1 (130) + 1 / L21 (131)))))] ( 2)
Here, Z (PR1 (110)) is the impedance of the parallel arm resonator 110 of FIG. 12, and the L value of L21 (131) is half of L2 (131), that is, L21 (131) = L2 (131) / 2 and ω is ω = 2.0 * π * f where f is a frequency, and Z (SR1 (100)) is ½ of the impedance of the series arm resonator 100 of FIG.

  Normally, the characteristics of the circuit of FIG. 12 are evaluated by the characteristics of the lattice circuit of FIG. That is, the operation transmission coefficient (characteristic SF of the circuit of FIG. 12) of the lattice circuit of FIG. 13 substitutes the values (ZF, ZS) of the equations (1) and (2) into the following equation (3). Is required.

SF = (1 + ZF) (1 + ZS) / (ZF−ZS) (3)
Therefore, the attenuation characteristic α (ω) is given by equation (4).

α (ω) = 20 * LOG (ABS (SF)) (4)
Here, ABS (SF) represents an absolute value in (), and * represents multiplication.

  That is, the attenuation pole frequency is formed in the attenuation band by L, or the increase in attenuation occurs by L when either of the following conditions (5A) or (5B) is satisfied.

ZF = ZS (5A)
ZS = ∞ (5B)
A feature of the present embodiment is that L (L1 or L21) is included in ZF and ZS in the expressions (1) and (2). That is, by including L in ZF and ZS, the attenuation pole frequency is formed in the attenuation band by satisfying the condition (5A), or the attenuation pole frequency is set in the attenuation band by satisfying the condition (5B). This is a case where the amount of attenuation increases. This point will be described using an equivalent LC circuit of a SAW resonator as shown in FIG.

  When the equivalent LC circuit of FIG. 14 is used, Expression (1) and Expression (2) are given by Expression (6) and Expression (7).

ZF = (S ^ 2 + ω1 ^ 2 + S ^ 2 * L11 * Cf * (S ^ 2 + ω2 ^ 2)) / (S * Cf * (S ^ 2 + ω2 ^ 2)) (6)
ZS = (S ^ 2 + ω3 ^ 2 + S ^ 2 * L22 * Cs * (S ^ 2 + ω4 ^ 2)) / (S * Cs * (S ^ 2 + ω4 ^ 2)) (7)
Here, L11 = L1 (130), 1 / L22 = 1 / L1 (130) + 1 / L21 (131), Cf = capacity of parallel arm, Cs = capacity of series arm, ω1 = zero point of parallel arm (ie impedance) Ω2 = the pole point of the parallel arm (that is, the point where the impedance is maximized or minimized), ω3 = the zero point of the series arm, and ω4 = the pole point of the series arm.

  That is, the frequency that gives the attenuation pole using the expression (6), the expression (7) and the above-described (5A) which is the condition for forming the attenuation pole is obtained from the following expression (8).

Cf * (S ^ 2 + ω2 ^ 2) * (S ^ 2 + ω1 ^ 2 + S ^ 2 * L11 * Cf * (S ^ 2 + ω2 ^ 2)) = (S ^ 2 + ω3 ^ 2 + S ^ 2 * L22 * Cs * (S ^ 2 + ω4 ^ 2)) * Cs * (S ^ 2 + ω4 ^ 2)) (8)
Note that ^ 2 means the square of the immediately preceding numerical value.

  Here, the feature of this embodiment is that L11 and L22 are included in Expression (8). In particular, due to the presence of L22, the attenuation pole frequency obtained from Equation (8) becomes the low-frequency side attenuation band of the pass band.

  Next, this embodiment is compared with the conventional SAW filter LA shown in FIG. The ZF and ZS related to the SAW filter LA are given by Expression (9) and Expression (10).

ZF = Z (PR1 (110)) + jωL11 (130) (9)
ZS = 1 / ((1 / Z (SR1 (100)) + 1 / (1 / Z (PR1 (110))) (10)
Here, Z (PR1 (110)) is the impedance of the parallel arm resonator 110 shown in FIG. 6, and L11 (130) = 2.0 * L1 (130), where ω is a frequency f and ω = 2. It is given by 0 * π * f, and Z (SR1 (100)) is an impedance value corresponding to ½ of the series arm resonator 110 of FIG.

  As is clear from the comparison of the corresponding expressions, the major difference between the SAW filter 10 of this embodiment and the SAW filter LA of FIG. 6 is whether or not L is included in ZS.

  In this case, the pole frequency corresponding to the equation (8) is obtained from the following equation (11).

Cf * (S ^ 2 + ω2 ^ 2) * (S ^ 2 + ω1 ^ 2 + S ^ 2 * L11 * Cf * (S ^ 2 + ω2 ^ 2)) = Cs * (S ^ 2 + ω3 ^ 2) * (S ^ 2 + ω4 ^ 2)) ... (11)
Using the condition ZF = ZS of the attenuation pole formation ((5A)), the frequency to give the attenuation pole is obtained from the above equation (8) in the case of this embodiment, and in the case of the conventional SAW filter LA shown in FIG. It is obtained from the formula (11).

  Comparing the two equations, equation (8) contained L11 and L22, whereas equation (11) contained only L11. For this reason, in the conventional SAW filter LA, an attenuation pole is formed in the high band side attenuation region of the pass band.

  On the other hand, FIG. 15 shows a characteristic simulation result using the L values of the three inductances L1 to L3 in the two-terminal pair circuit 31 as parameters in the polarized SAW filter 10 of the present embodiment. Here, the characteristic curve of L = 0 on FIG. 15 corresponds to the filter characteristic of the conventional two-stage π-type ladder SAW filter shown in FIG.

  FIG. 15 shows the following (1) to (3) as compared with the conventional two-stage π-type ladder SAW filter shown in FIG.

  (1) Due to L1 (130), L2 (131), and L3 (132), the (low band) attenuation poles LP21 to LP are placed in the low band side attenuation band and the high band side attenuation band of the pass band (about 860 MHz to about 900 MHz). LP41, LP22 to LP42 and (high band) attenuation poles HP21 to HP41, HP22 to HP42 are formed.

  Of these, the low-frequency attenuation poles LP21 and LP22 correspond to the case of L = 0.1 nH, the low-frequency attenuation poles LP31 and LP32 correspond to the case of L = 0.2 nH, and the low-frequency attenuation poles LP41 and LP42 have L = This corresponds to the case of 0.4 nH. Similarly, the high-frequency attenuation poles HP21 and HP22 correspond to the case of L = 0.1 nH, the high-frequency attenuation poles HP31 and HP32 correspond to the case of L = 0.2 nH, and the high-frequency attenuation poles HP41 and HP42 are L This corresponds to the case of = 0.4 nH.

  (2) Further, as shown in FIG. 8, due to these attenuation poles, a 30 dB attenuation width indicating the width of the frequency band where the attenuation amount is 30 (dB) or more is, for example, L = 0.2 (in this embodiment). In the case of (nH), the frequency is 54.5 (MHz) in the low-band attenuation band and 36.5 (MHz) in the high-band attenuation band. On the other hand, the conventional ladder-type SAW filter shown in FIG. 2 has 43.5 (MHz) in the low-band attenuation band and 35.0 (MHz) in the high-band attenuation band. This embodiment is wider by 11.5 (MHz) in the low-frequency attenuation band and wider by 1.5 (MHz) in the high-frequency attenuation band, compared to the conventional ladder-type SAW filter, High attenuation characteristics can be obtained.

  As is clear from FIG. 15, the 30 dB attenuation width in the present embodiment shows a tendency to increase as the L values of L1 to L3 increase.

  (3) Furthermore, as is apparent from FIG. 15, the slope between the passband and the attenuation band does not change even when the L values of L1 to L3 change, and is sufficiently steep.

  At the actual product level, the filter characteristics required for the SAW filter are determined in consideration of the relationship with the amplifier and modulator incorporated in the mobile communication device terminal together with the SAW filter. According to the polarized SAW filter of the embodiment, it is possible to cope with such consideration.

(A-3) Effect of First Embodiment According to the present embodiment, two attenuation poles are formed in the high band side attenuation band and the low band side attenuation band of the pass band by the two-terminal pair circuit (31). However, the attenuation due to the change of the formed attenuation pole is sufficiently large not only in the high-frequency attenuation band but also in the low-frequency attenuation band.

  This increases the possibility of satisfying the requirement standard for the high attenuation amount of the high band side attenuation band of the pass band and the requirement standard for the low band attenuation band of the pass band.

  In addition, in the present embodiment, such a filter characteristic can be realized by using a downsized SAW filter that uses a sufficiently small L-value inductance, which is also excellent in terms of feasibility.

  Further, as described above, the filter characteristics of this embodiment are sufficiently steep.

  Considering these points, for example, in the above-described example of the US CDMA system, when the polarized SAW filter of this embodiment is applied as a reception filter, sufficiently good filter characteristics can be obtained. Reception quality is improved.

  Of course, as described above, the polarized SAW filter of the present embodiment has excellent characteristics even when used as a transmission filter.

(B) Second Embodiment Hereinafter, only differences between the present embodiment and the first embodiment will be described.

(B-2) Configuration and Operation of Second Embodiment FIG. 16 shows a circuit diagram of the SAW filter 40 of the present embodiment. The SAW fill 40 is a filter corresponding to the SAW filter 10.

  In FIG. 16, the functions of the respective parts given the same reference numerals as in FIG. 1 correspond to those in FIG. 1.

  Therefore, the SAW filter 40 has a configuration in which a series arm resonator SR2, a parallel arm resonator PR3, an inductance L4, and connection points P7 and P8 are added to the SAW filter 10.

  Here, the series arm resonator SR2 is the same SAW resonator as the series arm resonator SR1, and the parallel arm resonator PR3 is the same SAW resonator as the parallel arm resonator PR1 or PR2. Further, the inductance L4 is the same inductance as the L1 to L3.

  That is, the polarized SAW filter 40 is composed of a two-terminal pair circuit forming a four-stage π-type ladder-type SAW filter and three Ls (L1 (120), L2 (121), L3 (122)). A two-terminal pair circuit is configured by connecting them in series.

  Also, in FIG. 17 showing the mounting example 40A corresponding to the circuit diagram of FIG. 16, the function of each part given the same reference numerals as in FIG. 11 is the same as FIG.

  That is, the mounting example 40A in FIG. 17 is different from the mounting example 10A in FIG. 11 in that the series arm resonator SR2 (101), the parallel arm resonator PR3 (112), the inductance L4 (42), and the pads 41 and 43. Is added.

  Again, the bonding wire 42 functions as the inductance L4.

  In the layout, the electrode connected to the pad 12 by the bonding wire 13 is not the electrode 14A but the electrode 14C.

  In the SAW filter 40 of this embodiment, as shown in FIG. 9, the cross length and logarithm of each SAW resonator are selected.

  FIG. 18 shows a characteristic simulation result using L as a parameter using the intersection length and logarithm of FIG. FIG. 10 shows changes in the attenuation pole and 30 (dB) attenuation width in the low-frequency attenuation band and the high-frequency attenuation band due to changes in L.

  As is apparent from FIGS. 10 and 18, attenuation poles are formed by the L values of L1 to L4 in the low band side attenuation band and the high band side attenuation band of the pass band. For example, the L value is 0.5 (nH ), The attenuation poles in the low-frequency attenuation band are 851.5 MHz (this corresponds to the point LP81 on FIG. 18) and 841.0 MHz (this corresponds to the point LP82 on FIG. 18).

  Since there are two attenuation poles in this way, when the 30 dB attenuation width is L = 0.5 (nH), 20.0 (MHz) in the low-frequency attenuation band and 12 in the high-frequency attenuation band. 0.0 (MHz), which is 7 (MHz) wider in the low-frequency attenuation band and 2 (MHz) wider in the high-frequency attenuation band than the conventional ladder-type SAW filter.

  That is, it can be seen that the attenuation characteristics in the low-frequency attenuation band and the high-frequency attenuation band are greatly improved, and the standard is satisfied.

  In the filter characteristics of FIG. 18, the slopes of the passband and attenuation band do not change even when the L values of L1 to L4 change, and are sufficiently steep.

(B-2) Effects of Second Embodiment As described above, according to the present embodiment, it is possible to obtain substantially the same effects as those of the first embodiment.

  In addition, in this embodiment, the attenuation characteristics of the low-frequency attenuation band and the high-frequency attenuation band of the pass band can be controlled relatively freely.

(C) Other Embodiments In the first and second embodiments described above, many specific numerical values are shown for the sake of brevity, but these are merely examples and the application of the present invention. The range is not limited by these numerical values.

  Therefore, although the L value described above can be changed to various values, the present invention can be realized with a small L value.

  Regardless of the first and second embodiments, as a matter of course, a T-type two-terminal pair circuit may be used instead of the π-type two-terminal pair circuit as the two-terminal pair circuit.

  Moreover, the mounting example of FIG. 17 of the second embodiment can be replaced with the mounting example of FIG. 19 as an example.

  In the mounting example of FIG. 19, the electrode pattern 50 is used as an inductance instead of the bonding wire 17 (L2).

  In the mounting example of FIG. 19, an example in which a part of the plurality of inductances existing in the two-terminal pair circuit is configured by an electrode pattern is shown. Of course, it may be configured by a pattern.

  Thus, the two-terminal-pair inductor of the present invention is suitable for realization with a multilayer substrate package.

1 is a circuit diagram of a polarized SAW filter according to a first embodiment. It is a circuit diagram of a conventional ladder-type SAW filter. It is operation | movement explanatory drawing of a SAW filter. It is operation | movement explanatory drawing of a SAW filter. It is operation | movement explanatory drawing of a SAW filter. It is a circuit diagram of a conventional polar SAW filter. It is operation | movement explanatory drawing of the polarized SAW filter concerning 1st Embodiment. It is operation | movement explanatory drawing of the polarized SAW filter concerning 1st Embodiment. It is operation | movement explanatory drawing of the polarized SAW filter concerning 2nd Embodiment. It is operation | movement explanatory drawing of the polarized SAW filter concerning 2nd Embodiment. It is the schematic which shows the example of mounting of the polarized SAW filter concerning 1st Embodiment. It is operation | movement explanatory drawing of the polarized SAW filter concerning 1st Embodiment. It is operation | movement explanatory drawing of the polarized SAW filter concerning 1st Embodiment. It is operation | movement explanatory drawing of the polarized SAW filter concerning 1st Embodiment. It is operation | movement explanatory drawing of the polarized SAW filter concerning 1st Embodiment. FIG. 6 is a circuit diagram of a polarized SAW filter according to a second embodiment. It is the schematic which shows the example of mounting of the polar SAW filter concerning 2nd Embodiment. It is operation | movement explanatory drawing of the polarized SAW filter concerning 2nd Embodiment. It is the schematic which shows another example of mounting of the polarized SAW filter concerning 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 40 ... Polarized SAW filter, 13, 15, 17-19 ... Bonding wire, 21 ... Piezoelectric substrate, 30, 31 ... Two-terminal pair circuit, 100, 110, 111 ... SAW resonator, L1-L4 ... Inductance, LP21 to LP41, LP22 to LP42, HP21 to HP41, HP22 to HP42 ... attenuation poles.

Claims (1)

A first SAW resonator connected between the first electrode and the second electrode; the first electrode; the second electrode; the third electrode; and the fourth electrode; A piezoelectric device in which a second SAW resonator connected to one electrode and the third electrode, and a third SAW resonator connected to the second electrode and the fourth electrode are formed. A conductive substrate;
A package having a plurality of package electrodes and mounting the piezoelectric substrate;
A bonding wire group consisting of a plurality of bonding wires;
The third electrode and the fourth electrode are connected to each other through the bonding wire group, and the third electrode, the fourth electrode, and the package electrode are supplied with a ground voltage. And a SAW filter package characterized by being connected to each other.

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